%I
%S 19,68,117,139,166,215,264,313,362,411,460,482,509,558,607,656,705,
%T 754,803,825,852,901,979,999,1048,1097,1146,1168,1195,1244,1293,1342,
%U 1391,1440,1489,1511,1538,1587,1636,1685,1734,1783
%N Numbers n such that string 2,5 occurs in the base 7 representation of n but not of n+1.
%t SequencePosition[Table[If[SequenceCount[IntegerDigits[n,7],{2,5}]>0,1,0],{n,2000}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 16 2020 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
